Mortgage rates dropped below 4 percent for the first time since November, providing more kindling to an already hot housing market as the crucial spring selling season gets under way, the Wall Street Journal reported today. The average rate on a 30-year fixed-rate mortgage dropped to 3.97 percent for the week ended April 20, from 4.08 percent a week earlier and 4.3 percent in mid-March, according to data released Thursday by mortgage company Freddie Mac. For most of 2016, mortgage rates, which generally move together with yields on the benchmark 10-year U.S. Treasury note, hovered just above 3.5 percent for the 30-year fixed-rate mortgage.